David Kirkpatrick

December 23, 2009

Dyeing graphene

I’ve done plenty of blogging on graphene, the world’s thinnest material at a single atom of carbon, and I’ve even posted an actual image of graphene. Now scientists at Northwestern University have found a way to actually dye the material — well, technically the method is more a reverse dyeing — but the result is a great reduction in cost when imaging graphene for certain applications.

From the link:

The useful tool is the dye fluorescein, and Jiaxing Huang, assistant professor of materials science and engineering at the McCormick School of Engineering and Applied Science, and his research group have used the dye to create a new imaging technique to view graphene, a one-atom thick sheet that scientists believe could be used to produce low-cost carbon-based transparent and flexible electronics.

Their results were recently published in the Journal of the American Chemical Society.

Being the world’s thinnest materials, graphene and its derivatives such as graphene oxide are quite challenging to see. Current imaging methods for graphene materials typically involve expensive and time-consuming techniques. For example,  (AFM), which scans materials with a tiny tip, is frequently used to obtain images of graphene materials. But it is a slow process that can only look at small areas on smooth surfaces.  (SEM), which scans a surface with high-energy electrons, only works if the material is placed in vacuum. Some  methods are available, but they require the use of special substrates, too.

Update: Here’s a press release on this exact topic. Find the full text of the release (plus images) below the fold. (more…)

February 15, 2009

Everquest and social research

My previous blog post was on using the internet for social research, and here is a study using Everquest II for just that on organizing networks in communities. Interesting work in the online social research area already.

The release from yesterday:

Surprising results: Virtual games players stick close to home

In the real world, tracking a person’s social network — which could include hundreds of contacts that serve different purposes — is nearly impossible.

But in online virtual games like EverQuest II, where tens of thousands of people leave digital traces as they chat with one another, perform quests together, form groups and buy and sell goods, researchers have found a gold mine of networking data.

That’s where social scientist and engineer Noshir Contractor comes in. Contractor, the Jane S. and William J. White Professor of Behavioral Sciences at the McCormick School of Engineering and Applied Science at Northwestern University, and his collaborators are studying nearly 60 terabytes of data from EverQuest II, a fantasy massive multiplayer online role-playing game where players complete quests and socialize with each other.

The researchers analyzed this data along with a survey of 7,000 players — making it one of the largest social science research projects ever performed, Contractor said.

Contractor will discuss their surprising results in a presentation titled “Social Drivers for Organizing Networks in Communities,” which will be part of the “Analyzing Virtual Worlds: Next Step in the Evolution of Social Science Research” symposium from 8:30 to 10 a.m. Saturday, Feb. 14, at the American Association for the Advancement of Science (AAAS) Annual Meeting in Chicago. The symposium will be held in Columbus GH, Hyatt Regency Chicago, 151 East Wacker Drive.

The group has mined the data logs from the game to look for “structural signatures” that indicate different kinds of social network configurations.

“We can see whom these players talked to, whom they played with, and all the other interactions and transactions they had,” Contractor said. “In many ways it’s a microcosm of our existence in the general social world.”

The researchers found that many players underestimate the amount of time they spend playing the games, and the number of players who say they are depressed is disproportionately high. They also found that women don’t like to play with other women but are generally the most dedicated and satisfied players. And players aren’t just teenagers — in fact, the average age of a player is substantially higher.

But what most surprised Contractor was that even though players could play the game with anyone, anywhere, most people played with people in their general geographic area.

“People end up playing with people nearby, often with people they already know,” Contractor said. “It’s not creating new networks. It’s reinforcing existing networks. You can talk to anyone anywhere, and yet individuals 10 kilometers away from each other are five times more likely to be partners than those who are 100 kilometers away from each other.”

Worldwide, nearly 45 million people play massive multiplayer online role-playing games like EverQuest II, and the amount of real-world money associated with virtual worlds would make it the seventh largest country in the world according to gross domestic product.

“This is not a trivial issue,” Contractor said. “Now that we have the computing power to study these networks, we can explore different theories about social processes on a scale that was never possible before.”

 

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November 20, 2008

Twisting electronics

One step closer to wearables.

The release:

Researchers make new electronics — with a twist

They’ve made electronics that can bend. They’ve made electronics that can stretch.

And now, they’ve reached the ultimate goal — electronics that can be subjected to any complex deformation, including twisting.

Yonggang Huang, Joseph Cummings Professor of Civil and Environmental Engineering and Mechanical Engineering at Northwestern University’s McCormick School of Engineering and Applied Science, and John Rogers, the Flory-Founder Chair Professor of Materials Science and Engineering at the University of Illinois at Urbana-Champaign, have improved their so-called “pop-up” technology to create circuits that can be twisted. Such electronics could be used in places where flat, unbending electronics would fail, like on the human body.

Their research is published online by the Proceedings of the National Academy of Sciences (PNAS).

Electronic components historically have been flat and unbendable because silicon, the principal component of all electronics, is brittle and inflexible. Any significant bending or stretching renders an electronic device useless.

Huang and Rogers developed a method to fabricate stretchable electronics that increases the stretching range (as much as 140 percent) and allows the user to subject circuits to extreme twisting. This emerging technology promises new flexible sensors, transmitters, new photovoltaic and microfluidic devices, and other applications for medical and athletic use.

The partnership — where Huang focuses on theory, and Rogers focuses on experiments — has been fruitful for the past several years. Back in 2005, the pair developed a one-dimensional, stretchable form of single-crystal silicon that could be stretched in one direction without altering its electrical properties; the results were published by the journal Science in 2006. Earlier this year they made stretchable integrated circuits, work also published in Science.

Next, the researchers developed a new kind of technology that allowed circuits to be placed on a curved surface. That technology used an array of circuit elements approximately 100 micrometers square that were connected by metal “pop-up bridges.”

The circuit elements were so small that when placed on a curved surface, they didn’t bend — similar to how buildings don’t bend on the curved Earth. The system worked because these elements were connected by metal wires that popped up when bent or stretched. The research was the cover article in Nature in early August.

In the research reported in PNAS, Huang and Rogers took their pop-up bridges and made them into an “S” shape, which, in addition to bending and stretching, have enough give that they can be twisted as well.

“For a lot of applications related to the human body — like placing a sensor on the body — an electronic device needs not only to bend and stretch but also to twist,” said Huang. “So we improved our pop-up technology to accommodate this. Now it can accommodate any deformation.”

Huang and Rogers now are focusing their research on another important application of this technology: solar panels. The pair published a cover article in Nature Materials this month describing a new process of creating very thin silicon solar cells that can be combined in flexible and transparent arrays.

 

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